Stackable chair



FIG. 1 is a perspective view of the design, said view being taken from above and from the right side;

FIG. 2 is a left side of the design;

FIG. 3 is a front view of the design;

FIG. 4 is a top view of the design; and,

FIG. 5 is a rear view of the design.

FIGS. 2 through 5 have been shown on a reduced scale with respect to FIG. 1. 

The ornamental design for a stackable chair, as shown and described. 